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Hi :)
I recently bought a Beomaster 900M along with some speakers. It semi-worked when I got it, but the right side speaker had a lower volume and was lacking bass.
Last night I fiddled around with the stereo and tried to adjust the balance via the balance-adjuster on the back, which resulted in almost no sound in both speakers.
Today I decided to try my luck at replacing the balance-potmeter, since I thought that might fix the problem.
I replaced the original potmeter:
http://imgur.com/a/nQgGE
With this one:
http://imgur.com/a/sYWe6
But that only made things worse...
Now, when I turn on the stereo, all I hear a loud buzzing and this resistor gets smoking hot:
http://imgur.com/a/2E1hR
I'm not sure where to go from here. I have experience working with old electronics (pinball machines), but I currently don't know anything about stereos.
Any help would be much appreciated :)
So I just tried disconnecting the AD-139(1) output transistor, which made the buzzing stop. The stereo is operational with this transistor disconnected, and I can use the new potmeter to adjust the balance.
With the transistor disconnected, there is no output to the right speaker and the resistor at 641 gets really hot after about a minute.
If I reconnect AD-139(1) the problem reverts to the one stated in the original post.
AD-139(1) has been replaced by an AD-162 at some point btw.
http://imgur.com/a/kFYlf
I found this on beocentral.com
"Beomaster 900
20th October 2009
This receiver gave no results and was getting hot because one of the AD139 output transistors was short circuit. After replacing this the set worked but there was a hum in the background and the regulated supply to the amplifier was high at 27V (it should be 22V). The SP1446 regulator transistor had also been damaged, replacing this removed the hum and allowed the output voltage to be set up correctly.
The original transistors used in the Beomaster 900 are becoming difficult to find but the AD139 can be replaced by an AD162 (providing both transistors in the affected channel are replaced) and the SP1446 by and AD149, both of which are still widely available. [Beomaster 900K, Beomaster 900M]"
Could it be the same issue I'm having?
I can't find a good source for AD162 and AD149 transistors in Europe though..
Anybody?